During the spring of 1985 Delone Catholic left the conference and in 1992, after 10 years of competition, the MPC added 8 additional schools to the mix; Bermudian Springs, Biglerville, Fairfield, Gettysburg, Greencastle-Antrim, James Buchanan, Scotland, and Waynesboro, bringing its total membership to thirty-four.

During the spring of 2004 three schools indicated their intentions of leaving the Conference. So, while Bermudian Springs, Biglerville, and Fairfield departed, Altoona, Hollidaysburg, and State College were admitted for the purpose of competing in football only in the AAAA classification beginning in the fall of 2004..

At the conclusion of the 2005-2006 school year Hollidaysburg departed from its football only status as did Altoona at the conclusion of the 2008-2009 school year. Also, as a result of state budget problems, The Scotland School for Veterans Children was closed by the Governor at the conclusion of the 2008-2009 school term..

In 2006-2007 the Mid Penn Conference began its 25th year as an athletic conference which was celebrated on Thursday, April 10, 2008 at the Hotel Carlisle off the Harrisburg Pike, Carlisle, PA.

In 2012-2013 the Mifflin County School District and State College were admitted into the Mid Penn Conference for the purpose of competing in the High School Divisions in all sports, while at the end of the 2013-2014 school year Gettysburg and Susquenita left the conference.